1. Field
Aspects of the present disclosure relate to a composition including a compound having a fluorine functional group, a polymer of the composition, an electrode and an electrolyte membrane for a fuel cell that include the composition or the polymer, and a fuel cell including at least one of the electrode and the electrolyte membrane.
2. Description of the Related Art
Fuel cells that include a polymer electrolyte membrane operate at relatively low temperatures and may be manufactured in small sizes. Thus, such fuel cells are expected to be used as energy sources in electric vehicles and in distributed generation systems. Perfluorocarbon sulfonic acid-based polymer membranes, such as NAFION membranes (available from E.I. du Pont de Nemours and Company), are commonly used as polymer electrolyte membranes for fuel cells.
However, such polymer electrolyte membranes should be humidified in order to sufficiently conduct protons. In addition, to enhance cell system efficiencies, polymer electrolyte membranes should be operated at high temperatures, i.e., at least 100° C. However, the moisture in the polymer electrolyte membrane is evaporated and depleted at such temperatures, which reduces the effectiveness thereof.
To address such problems and/or other problems in the related art, non-humidified electrolyte membranes, which may operate at temperatures of at least 100° C. without humidification, have been developed. For example, polybenzimidazole doped with phosphoric acid has been disclosed as a material for a non-hydrated electrolyte membrane.
In low temperature perfluorocarbonsulfonate polymer electrolyte membrane fuel cells, in order to prevent defective gas diffusion in an electrode (in particular in a cathode), which may be caused by water (product water) generated during electric power production in the electrode, hydrophobic electrodes including polytetrafluoroethylene (PTFE) have been used.
In addition, phosphoric acid fuel cells, which operate at temperatures of from 150 to 200° C., include a liquid phosphoric acid electrolyte. However, the liquid phosphoric acid included in a large amount in electrodes interferes with gas diffusion in the electrodes. Therefore, an electrode catalyst layer that includes a polytetrafluoroethylene (PTFE) waterproofing agent, which prevents fine pores in the electrodes from being clogged by the phosphoric acid, has been used.
In addition, in fuel cells including a polybenzimidazole (PBI) electrolyte membrane, which uses a phosphoric acid as a non-humidified electrolyte, in order to reduce contact between electrodes and the electrolyte membrane, a method of impregnating the electrodes with a liquid phosphoric acid has been used, and a method of increasing the loading amount of metal catalysts has been used. However, such fuel cells do not exhibit improved properties.
In addition, when a phosphoric acid-doped solid polymer electrolyte is used, and air is supplied to the cathode, the activation time thereof is about 1 week, even when an optimized electrode composition is used. Although the performance of the solid polymer electrolyte may be improved, and the activation time may be shortened, as air supplied to the anode is replaced with oxygen, this replacement is undesirable for commercial use. Furthermore, an electrolyte membrane prepared using a homopolymer of PBI does not have sufficient mechanical properties, chemical stability, and capability to retain phosphoric acid at a high temperature.